In a multi-cavity injection molding apparatus having a hot runner manifold for delivering a melt stream of moldable material to a plurality of hot runner nozzles. Heat expansion can cause the manifold to warp. As a result, the distance between the lower surface of the manifold and each of a plurality of mold cavities varies and thus each nozzle is subjected to unique operating conditions depending on the nozzle's location relative to the manifold. As such, the thermal expansion results in a variable sealing force being applied to both the interface between the nozzle and manifold and the nozzle and mold gate. If the manifold “floats” where a head of the nozzle is in contact with the lower surface of the manifold but not attached to it, an uneven sealing condition may allow the pressurized melt to leak at the interface between the manifold and each nozzle and/or in the mold gate area around the nozzle seals. If the nozzles are threaded into the manifold, an uneven sealing condition may still allow the pressurized melt to leak in the mold gate area.
Many nozzle designs rely on thermal expansion of the nozzle to provide sealing at the mold gate and at the nozzle/manifold interface, which can be aided by the use of one or more pressure disks between a back plate and an upstream surface of the manifold. However in an injection molding apparatus having edge gated nozzles, which are nozzles having a number of radially extending or horizontal tips, the radially extending tips are generally axially fixed in position to align with the mold gate and therefore the conventional edge gated nozzle may be prevented from thermal expansion in a longitudinal direction. With the radially extending tips axially fixed in position, leakage may occur between the tip and mold gate or the tip and nozzle due to the large amount of force acting on the tips under operating conditions. Leakage may also occur at the nozzle and manifold interface because in a conventional edge gated system that does not allow for thermal expansion of the nozzle, pressure disks that usually provide sealing support at this interface are ineffective, as such pressure disks do not work without the changes in force experienced by thermal expansion of the nozzle.
Although solutions exist in the art for addressing sealing in edge gated injection molding systems, a need still exists for a sealing connection between a hot runner manifold and an edge gated nozzle that accommodates thermal expansion of the nozzle and some deflection of the manifold without causing a variable or excessive force being applied between the nozzle and the manifold or the nozzle and a mold gate of an injection molding system.